package com.young.security.md5;

import java.security.MessageDigest;

public class MD5Utils {

  private String inStr;
  private MessageDigest md5;

  /**
   * Constructs the MD5 object and sets the string whose MD5 is to be
   * computed.
   *
   * @param inStr the <code>String</code> whose MD5 is to be computed
   */
  public MD5Utils(String inStr) {
    this.inStr = inStr;
    try {
      this.md5 = MessageDigest.getInstance("MD5");
    } catch (Exception e) {
      System.out.println(e.toString());
      e.printStackTrace();
    }
  }

  public static String md5(String key) {
    if (key == null) {
      return "";
    }
    MD5Utils utils = new MD5Utils(key);
    return utils.compute();

  }

  /**
   * Computes the MD5 fingerprint of a string.
   *
   * @return the MD5 digest of the input <code>String</code>
   */
  public String compute() {
    // convert input String to a char[]
    // convert that char[] to byte[]
    // get the md5 digest as byte[]
    // bit-wise AND that byte[] with 0xff
    // prepend "0" to the output StringBuffer to make sure that we don't end
    // up with
    // something like "e21ff" instead of "e201ff"

    char[] charArray = this.inStr.toCharArray();

    byte[] byteArray = new byte[charArray.length];

    for (int i = 0; i < charArray.length; i++) {
      byteArray[i] = (byte) charArray[i];
    }

    byte[] md5Bytes = this.md5.digest(byteArray);

    StringBuffer hexValue = new StringBuffer();

    for (int i = 0; i < md5Bytes.length; i++) {
      int val = ((int) md5Bytes[i]) & 0xff;
      if (val < 16) {
        hexValue.append("0");
      }
      hexValue.append(Integer.toHexString(val));
    }

    return hexValue.toString();
  }

  public static void main(String[] args) {
    MD5Utils md5 = new MD5Utils("123456");
    String postString = md5.compute();
    System.out.println("加密后的字符:" + postString.length());
    if (postString.equals("900150983cd24fb0d6963f7d28e17f72")) {
      System.out.println("true");
    } else {
      System.out.println("false");
    }
  }
}
